scholarly journals Feeding Ecology of Short-Toed Snake-Eagle (Circaetus gallicus [Gmelin, 1788]) in the Montados of Iberian Peninsula

2020 ◽  
Vol 28 (2) ◽  
pp. 155-179
Author(s):  
Nuno Onofre ◽  
Luís Sampaio
Keyword(s):  
Relative Abundance ◽  
Diet Composition ◽  
Prey Species ◽  
Prey Selection ◽  
Prey Type ◽  
Generalist Predator ◽  
Important Prey ◽  
Psammodromus Algirus ◽  
Circaetus Gallicus ◽  
Water Snakes

The diet of Short-toed Snake-eagle (Circaetus gallicus) during the breeding season in an area dominated by cork and holm oak parkland forests (Montados) was analyzed in this study. As expected, results showed that snakes are the dominant prey in the diet of this eagle, comprising up to 92.5% of the identified items, if potential secondary prey species were excluded. The Montpellier Snake (Malpolon monspessulanus) was the most consumed one (42.2%), followed by the Ladder Snake (Zamenis scalaris) (28.0%), and the water snakes (Natrix spp.) (14.2%). According to the same criteria, lizards (mainly Psammodromus algirus) and mammals represent between 4.8 and 2.2%, respectively. Other animals such as pond turtle and amphibians are irregular prey (<1%), and no bird remains were found at all. Short-toed Snake-eagle is usually referred as a stenophagic predator where snakes are by far its most important prey type, and where within this taxonomic group it behaves as a generalist predator. In this study this premise was then tested comparing the relative abundance of the snake species with their proportion in the diet composition of the eagle in order to know whether or not prey selection exists with regard to the species of snakes in this region. Results point to a quite plausible "preference" for the Ladder Snake and an "avoidance" for the smooth snakes group (Macroprotodon brevis/Coronella girondica), and possibly for the Horseshoe Whip (Hemorrhois hippocrepis). The avoidance to the Horseshoe Whip must be indirect and habitat related, while in relation to the two smooth snakes it may be due in large extend to its small size, in particular.

Diet composition and prey selection in the lizard Lacerta monticola

1991 ◽  
Vol 69 (7) ◽  
pp. 1728-1735 ◽  
Author(s):  
Valentin Pérez-Mellado ◽  
Dirk Bauwens ◽  
Martin Gil ◽  
Fátima Guerrero ◽  
Miguel Lizana ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Diet Composition ◽  
Prey Availability ◽  
Prey Selection ◽  
Selection Models ◽  
Important Prey ◽  
Activity Season ◽  
Individual Prey

We studied diet composition and prey selection in the lizard Lacerta monticola throughout its activity season. The most important prey groups in terms of numbers were Coleoptera, Diptera, Formicidae, and Araneae. Comparison of diet composition in the adult lizards with estimates of prey availability indicated that lizards exhibited precisely defined patterns of prey selection. Electivities were negative for prey < 3 mm in length and generally positive for larger prey, despite the higher relative abundance of the former group in the environment. Electivity scores for individual prey taxa were positively correlated with their length, and lizards preferentially consumed larger individuals belonging to the taxa containing smaller animals. Relative availability of the four major prey taxa fluctuated considerably throughout the year. In spite of these changes, monthly rates of consumption of Araneae and Diptera remained almost constant. Variations in monthly electivity scores were negatively correlated with relative availability of three (Coleoptera, Diptera, and Araneae) of the four major prey taxa. These results fit the predictions of prey-selection models based on nutrient constraints.

Diet and prey selection dynamics of Cancer polyodon in three different habitat types in Tongoy Bay, Chile

2004 ◽  
Vol 84 (4) ◽  
pp. 751-756 ◽  
Author(s):  
Rafael I. León ◽  
Wolfgang B. Stotz
Keyword(s):  
Prey Species ◽  
Prey Availability ◽  
Prey Selection ◽  
Feeding Habits ◽  
Habitat Types ◽  
Important Prey ◽  
Selection Dynamics ◽  
Argopecten Purpuratus ◽  
Sea Grass ◽  
Main Factors

Feeding dynamics of Cancer polyodon was studied, by comparing the diets of three size-classes of the crab to environmental abundance of prey species in three habitats in Tongoy Bay, Chile (30°S). In the sea grass and sand–gravel habitats cannibalism was observed, the small C. polydon being actively selected as the main prey in spite of their lower abundance compared with other crustaceans. In the mud habitat the scallop Argopecten purpuratus was the most important prey, being actively selected although occurring at low relative abundance. Cancer polyodon showed plasticity in feeding habits, adapting to differential prey availability, but always selecting certain species independently of their abundance in each habitat. Accessibility, more than the abundance of the prey, seem to be the main factors influencing prey selection.

scholarly journals Diet of Teius oculatus (Sauria, Teiidae) in southern Brazil (Dom Feliciano, Rio Grande do Sul)

2007 ◽  
Vol 97 (1) ◽  
pp. 31-35 ◽  
Author(s):  
Lize Helena Cappellari ◽  
Thales de Lema ◽  
Paulo Prates Jr. ◽  
Carlos Frederico Duarte da Rocha
Keyword(s):  
Diet Composition ◽  
Stomach Contents ◽  
Prey Type ◽  
Adult Males ◽  
Rio Grande Do Sul ◽  
Importance Value Index ◽  
Importance Value ◽  
Important Prey ◽  
Adult Females ◽  
Males And Females

We analyzed stomach contents of 58 specimens of Teius oculatus (D'Orbigny & Bibron, 1837) (20 adult males, 17 adult females and 21 juveniles) captured in Dom Feliciano, RS, Brazil, to evaluate diet composition and sexual and ontogenetic variations in prey consumption. Diet was composed of 15 prey categories, all arthropods. Orthoptera was the most frequent prey type. Quantitatively, termites were the most important prey item (59.5%). There were no significant differences between the diets of adult males and females. Ontogenetic differences were found, mainly concerning volume of prey consumed. Adult lizards ingested significantly larger prey than juveniles (U = 170.00; p < 0.001). Juveniles, although having a comparatively less diverse diet (10 prey types) consumed a larger number of items (45.7% of total). Diet similarity was higher between juveniles and adult males (Ojk = 0.97) and prey diversity was higher in the diet of adult females (H' = 2.65). Based on importance value index the most important item in the diet of T. oculatus was Orthoptera. We conclude that T. oculatus in Dom Feliciano has a relatively generalized diet and it is an opportunist lizard, feeding on arthropods, mainly insects.

Influence of Prey Type on Growth of Young Yellow Perch (Perca flavescens)

1987 ◽  
Vol 44 (11) ◽  
pp. 2028-2033 ◽  
Author(s):  
John L. Confer ◽  
Gary J. Lake
Keyword(s):  
Yellow Perch ◽  
Prey Species ◽  
Prey Selection ◽  
Perca Flavescens ◽  
Prey Type ◽  
Equal Mass ◽  
Fish Growth ◽  
Oneida Lake ◽  
Species Mixture ◽  
Diet Type

Growth of age 0 + yellow perch (Perca flavescens) fed different zooplankton diets was examined in the laboratory during June and July 1983. Fish were fed an equal mass of diet types that varied with respect to prey species, mean length of the same prey species, and species mixture. Fish consumed all prey within 4 h of feeding. In four trials the ranking of diet type by fish growth was always Diaptomus sicilis > Oneida Lake tow sample > Daphnia spp. Differences in fish growth frequently varied by 50–300%. These differences suggest that nutritional processes, such as digestion or assimilation, will influence the optimal prey selection for, at least, small zooplanktivorous fish.

Interpreting Selectivity Indices Calculated from Field Data or Conditions of Prey Replacement

1987 ◽  
Vol 44 (9) ◽  
pp. 1529-1533 ◽  
Author(s):  
John L. Confer ◽  
Marianne V. Moore
Keyword(s):  
Relative Abundance ◽  
Prey Item ◽  
Field Data ◽  
Prey Selection ◽  
Prey Type ◽  
Neutral Selection ◽  
Field Samples ◽  
Linear Index ◽  
Selection For ◽  
The Impact

Indices of prey selection are compared empirically to clarify the kind of information each can provide and when the indices can be used appropriately. Emphasis is given to Chesson's alpha (α) and Strauss' Linear index (Li) because they are commonly used and represent two mathematically dissimilar approaches to measuring selection. Neutral selection for α and Li is not equivalent. For Li, neutral selection for a prey type occurs when selectivity equals the weighted (by relative abundance) average selectivity for all other prey types. For α, neutral selection equals the unweighted average for all prey types, which is equivalent to 1 divided by the number of prey types. Li and α respond differently to rare prey types. This is especially evident in field samples having large differences in relative prey abundances. Li values decrease as abundance of a prey type decreases in the environment, in contrast, α values often increase greatly as the proportional abundance of a prey type in the environment decreases. Consequently, α values, but not Li values, are often strongly influenced by the values for very rare prey, α values are sensitive to changes in the number of prey types, but not to changes in prey proportion. When the number of prey types is constant, α may be the most meaningful indicator of prey type preference. In contrast, Li values are sensitive to changes in prey proportions in the environment. When prey proportions are constant among experiments, Li is appropriate for measuring changes in the impact of a predator on a prey type and changes in selectivity relative to the average prey item. If number of prey types and prey proportions vary among experiments, Vanderploeg and Scavia's W or E* may be most appropriate.

scholarly journals Feeding habits of oriental sole (Brachirus orientalis) on the Bushehr coast of the Persian Gulf

2020 ◽  
Vol 28 (3) ◽  
pp. 175-185
Author(s):  
Dima Alghada ◽  
Yazdan Keivany ◽  
Fatemeh Paykan-Heyrati
Keyword(s):  
Coastal Waters ◽  
Persian Gulf ◽  
Diet Composition ◽  
Prey Species ◽  
Feeding Habits ◽  
Male And Female ◽  
Important Prey ◽  
Males And Females ◽  
The Persian Gulf ◽  
Prey Items

AbstractThe feeding habits of oriental sole, Brachirus orientalis (Bloch & Schneider) were investigated using 300 male and female specimens collected from coastal waters of Bushehr Province (Persian Gulf) between June 2015 and July 2016. The total length of females and males ranged from 16.2 to 38.5 cm and 14.1 to 29.1 cm, respectively. Of the total number of stomachs examined, 225 were empty (vacuity index = 77%). This index varied significantly over the year (P < 0.05), with maximum values in April and September and minimum in October and May. The B. orientalis diet was composed of nine prey species belonging to five classes. The most important prey items were Crustacea and Mollusca (Bivalvia and Gastropoda). Diet composition showed little seasonal variation, and Crustacea, Bivalvia, and Gastropoda were the most important prey items in all seasons. Sex did not appear to have any significant effects on dietary composition, and the main prey items were consumed by both males and females (P > 0.05).

Diet composition and prey selection of vendace Coregonus albula in the mesotrophic, temperate Lake Ostrowite (Northern Poland)

2008 ◽  
Vol 37 (1) ◽  
Author(s):  
Tomasz Kakareko ◽  
Paweł Napiórkowski ◽  
Jacek Kozłowski
Keyword(s):  
Diet Composition ◽  
Prey Selection ◽  
Temperate Lake ◽  
Coregonus Albula ◽  
Northern Poland ◽  
Mesotrophic Lake ◽  
Selection Of

Diet composition and prey selection of vendaceLake Ostrowite is a mesotrophic lake in Northern Poland 280.7 ha in area and 43 m deep at its deepest point. To study vendace (

PATTERNS OF GASTROPOD MOLLUSK PREDATION ON BIVALVE MOLLUSKS ALONG THE UPPER TEXAS GULF COAST

2018 ◽  
Vol 70 (1) ◽  
Author(s):  
Serena J. Randolph ◽  
Alan D. Maccarone
Keyword(s):  
Shell Thickness ◽  
Prey Species ◽  
Gulf Coast ◽  
Prey Selection ◽  
Drill Hole ◽  
The United States ◽  
Hole Diameter ◽  
Bivalve Mollusks ◽  
Collection Site ◽  
Drill Holes

Abstract Predation on bivalve mollusks by gastropod mollusks is common in coastal regions of the United States; however, few previous studies have examined whether drilling gastropods exhibit prey selection. In 2016, shells with small holes drilled by as many as two gastropod predators were collected at three sites separated by 30 km along the Texas Upper Gulf Coast on the Bolivar Peninsula (29° 40′N, 94° 90′W). The likeliest predators in these waters are the southern oyster drill (Stramonita haemastoma Linnaeus 1767) and the moon snail (Neverita duplicate Say 1822). Collected shells were identified to species and measurements were taken to examine statistical relationships between predators and prey species. These measurements included drill-hole diameter, shell thickness, drill-hole completeness, number of drill attempts, and collection site. Across the three locations, 17 different species of shells with drill holes were collected; of these, we focused on the ten most abundant species (n = 277 shells). The sample showed high variation in drill-hole diameter, shell thickness, and drill-hole completeness. Both the total number of holes and mean drill-hole diameter differed significantly among prey species (ANOVA, both P &lt; 0.0001). In addition, drill-hole diameter correlated directly with prey shell thickness (P &lt; 0.0001). Shells whose drill holes were complete were significantly thinner than shells with incomplete holes (P &lt; 0.0001). Mean prey shell thickness, mean drill-hole diameter, and mean number of drill holes all differed significantly by collection site (all P &lt; 0.0001). Ecological and morphological implications related to gastropod predation on mollusks are discussed.

Diet

2017 ◽  
Author(s):  
M.G.L. Mills ◽  
M.E.J. Mills
Keyword(s):  
Prey Species ◽  
Radio Tracking ◽  
Relative Occurrence ◽  
Important Prey ◽  
Individual Prey ◽  
Sibling Groups

Four methods were used to document the diet of cheetahs: incidental observations, radio tracking, tracking, spoor, and continuous follows. A combination of continuous follows and tracking spoor gave the best results. Steenbok were the most frequently killed species, but they did not dominate the diet in the same way as Thomson’s gazelle do in the Serengeti. Coalition males have a different diet profile from single males, single females, females with cubs, and sibling groups. For all but single males, the relative occurrence of prey species in the diet reflected its dietary importance in terms of kilograms of meat obtained. Gemsbok calves and adult ostrich were important prey for coalition males and springhares were important for single males. Three individual prey specializations for females were found; namely springbok specialists, steenbok/duiker specialists, and intermediates. Contrary to an earlier study, springbok were not found to be the most important prey species.

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